Ladders are used extensively in construction and maintenance tasks on construction sites and in buildings by a variety of trades and home do it yourself people. Used both indoors and out, ladders are often needed in locations and positions where the footing upon which they rest is uneven. Indoor stairwells present a particular problem for painters, electricians, etc. for accessing walls and ceilings. Out of doors uneven ground around a building or structure upon which work is to be performed poses a significant challenge in terms of safe ladder use. Many solutions to this problem have been devised including ladders with independently telescoping legs of various design, and ladder attachments that incorporate telescoping legs for the purpose of leveling a ladder on uneven surfaces.
Applicant is aware of patents regarding adjustable ladders and ladder attachments that provide support to the ladder so that each leg may adequately engage the supporting uneven surfaces:
PatentCountryInventorPatented1,609,257USALazear25 May 19263,998,293USARaia21 Dec. 19764,852,689USAErion01 Aug. 19894,984,655USAScherer, et al.15 Jan. 19915,476,153USADickerson,19 Dec. 1995et al.1,290,732CanadaVeness15 Oct. 19912,274,330CanadaBattenApp Jun. 3, 19991,499,300USAHayes24 Jun. 19241,862,171USABaker07 Jun. 19322,517,771USAStefano08 Aug. 19503,447,631USASmith03 Jun. 19694,607,726USADavis, et al.26 Aug. 19865,094,320USADeitz, et al.10 Mar. 19925,121,813USAFunston16 Jun. 19925,232,067USAGriffith03 Aug. 19935,542,497USAMacyszyn06 Aug. 19965,553,963USAHoy, et al.10 Sep. 19966,293,367USAGulseth25 Sep. 20016,374,947USANurkiewicz23 Apr. 20026,435,306USAStoneburg20 Aug. 20024,014,406USAEastonMar. 29, 1977
The fore-mentioned patents teach a variety of methods to make ladder legs adjustable in order to compensate for uneven supporting surfaces. Some require tools to attach the ladder leveling device, while others can be applied without tools. Some are mounted through the rung of a hollow rung ladder, while others are affixed to the outside of the rung or the main ladder frame or stiles. Some are easily removed while others are not. Some insulate the ladder primarily by means of a rubber foot pad, while others are not. Some are adjustable and positively secured, with some being easily quick and easy to adjust, while most are not. Many require permanent modification of the ladder being attached to.